The invention is based on a hydraulic brake system for a vehicle as defined herein. Such a brake system is already known from German Offenlegungsschrift 29 13 577, in which an apparatus for traction control associated with a driven wheel also serves as an anti-skid device. Since both this apparatus and a second apparatus of this type associated with the other driven wheel of the vehicle are supplied by a common pressure fluid source from a pressure fluid supply container, two magnetic valves switched by a control unit are needed in order to be able to perform both functions. To return the pressure fluid, a return line leading to the supply container is connected to the apparatus. An adjustable counter piston is also associated with the primary piston in order to attain an intermediate position of the stepped piston, in which this stepped piston keeps a spring-loaded check valve open in order to bypass the valve assembly between the master brake cylinder and the wheel brake. Moreover, a piston that can be acted upon by the pressure fluid is also provided in the apparatus, in order to actuate the valve assembly. The overall structure of the apparatus is complicated and accordingly expensive to produce, as well as vulnerable to malfunction.